Priscilla Riggioni Leonhardes, secretary general of the Costa Rican division of ICOLD, provides details on some of the country’s most impressive dam projects.
The Costa Rica hydropower sector continues to make headlines. According to the International Hydropower Association (IHA), at the end of 2016, total installed hydropower capacity in the Central American country stood at 2.12GW.
Costa Rica achieved 100% renewable electricity production for a total of 271 days, facilitated by the critical role of baseload energy from hydro generation.
In 2017, the Reventazón Hydroelectric Project in Costa Rica was the largest hydropower plant in Central America. This project has been classified as an example of international good practice in hydropower sustainability, according to the International Hydropower Association.
It was planned, designed and built by a 100% Costa Rican state company: Instituto Costarricense de Electricidad, and we are very proud of it.
Costa Rica hydropower: social, economic and environmental impact
The construction of the Reventazón project falls within the institutional responsibility for providing the country with a high quality supply of electricity, focused on sustainability and characterised by social and environmental respect.
In this context, the project has contributed to the development of 15 communities in Siquirres by means of 140 socio-environmental commitments included in the Environmental Impact Study (EIS). These actions aim to reverse, mitigate and compensate for the impact caused by the construction works.
Social management activities, such as training programmes on local development, production models, self-management, and environment, as well as the construction of education, health, and recreation centers, have improved the life quality of neighbours.
The biological, archaeological, forest, and environmental management programmes have generated valuable technical and scientific information, and they have always been in compliance with the guidelines established by the country.
In addition, the project’s socio-environmental management has incorporated actions promoted by the international banks that constitute the financing scheme, particularly the Environmental Offset Project for River Ecosystems, and the Barbilla-Destierro Biological Subcorridor, known as the “Jaguar Path”.
The Reventazón project’s legacy
- Benefits for 15 communities of Siquirres.
- 40 works related to road infrastructure, health, education and recreation.
- Temporary employment for 3,500 local workers
- A precursor project to women’s participation in the construction field.
- Creation of a plant nursery for reforestation with native species.
- Payment of an additional amount for environmental services (agreement with FONAFIFO).
- Ecological Blue Flag Award for three consecutive years.
- Identification and recording of archaeological pieces dating back 12,200 years.
- Integrated solid waste management.
Project description – the megaworks
- Diversion works allowed diverting the Reventazón river in order to build the dam. This set of structures comprises two diversion tunnels, a pre-cofferdam, a cofferdam and a secondary cofferdam. The diversion tunnels are located on the left bank, and they have an excavation diameter of 14m and an average length of 680m. The diversion system is designed for a peak flow rate of 4200m3/sec.
- Dam – a concrete-face rockfill dam with a fill volume of 9Mm3 (loose materials), forming a reservoir of bimonthly regulation. The minimum and maximum normal operation levels are 245 and 265 masl., respectively.
- Grout curtain – waterproofs the rock mass on which the dam is founded, sealing the fissures by means of deep holes filled with grout (a mixture of water and cement).
- Spillway – located on the right bank. Its components include an approach channel, four radial gates located in the control zone, a chute, and a ski-jump bucket.
- Intake – a front structure located on the right bank. It has a trashrack supported on the side walls. The intake gate is 7.5m wide and 9.4m high.
- Bottom outlet – a tunnel 614m in length with a discharge capacity of 500m3/sec at the maximum operation level of the reservoir. Since its main function is to evacuate sediments from the intake area, the bottom outlet is located very close to such a structure.
- Headrace tunnel – total length of 1,672m and a diameter of 9.4m. The rock cover varies from 0m (portals) to 153m.
- Penstock – supported by concrete saddles and anchor blocks. It is 905m long, and its diameter varies from 8.2m to 8.6m. A pipe bridge of 100m in length was built for a penstock section that crosses the Guayacán creek.
Reservoir water intake and dam.
- Surge tank– this steel cylinder of 27m in diameter and 5 m in height is lateral to the penstock line. A T-pipe is required to connect the tunnel to the surge tank and the penstock.
- Powerhouse – located on a terrace on the right bank of the Reventazón river, and houses four vertical-shaft Francis turbo generator units with a total capacity of 292MW. Water is released back into the river at 120masl.
- Ecological power plant – takes water from the reservoir at the spillway channel level and allows the downstream passage of a permanent compensatory flow of 15m3/sec.
- Substation – connects four transmission lines that derive from the current Tejar-Torito and Trapiche-Moín power lines.
- Location: Costa Rica (canton of Siquirres in the province of Limón)
- Construction started: April 2010
- Commercial operation: November 2016
- Reservoir area: 7km2
- Design flow rate: 240m3/sec
- Power capacity: 305.5M
- Equivalent production: 525,000 households.
The Sangregado Dam
The Sangregado Dam is part of the ARCOSA hydroelectric complex, composed of three cascade uses that together produce 363.30MW, making this complex the most important in the country in terms of hydroelectric generation capacity. It also corresponds to the largest potential energy reservoir that the country currently has.
Geographic Location: Tilarán, Guanacaste
- Start Operation: 1979
- Production Center: Arenal
- Power Capacity: 160MW
- Design Flow Rate: 97.5m3/sec.
- Exploited River: Arenal, Fortuna, Caño Negro, Cote, Chiquito and Aguas Gatas.
- Basin Area: 515.50 km2.
- Maximum level of operation: 546m asl.
- Minimum level of operation: 527m asl.
- Reservoir Area: 87 000m2
- Total Volume: 1901hm3
- Useful Volume: 1477hm3.
- Type: Earth Core Rockfill Dam
- Materials: Clay core impermeable and rockfill
- Crest Length: 1,012m
- Crest Width: 8m
- Height: 65m
- Base Width: 553
- Rockfill Volume: 4,660,000m3
- Spillway Type: Water well.
This full version of this article was originally published in International Water Power & Dam Construction.